The effects of branches on prepartum nest building in gilts with access tostraw

Sows farrowing in a semi-natural environment terminate nest building 1-7 h prior to parturition after having built a nest for which a variety of mater ials are used. No nest-building behaviour occurs during parturition and the sows remain lying in the nest throughout most of the farrowing. In contras t, many intensively housed sows are restless during farrowing. To investiga te whether gilts housed indoors would use branches for nest building and wh ether access to branches would affect the termination of nest building and parturient behaviour, we studied gilts housed individually in pens designed to stimulate natural nest building. The control group (n = 21) had unlimit ed access to straw and the experimental group (n = 21) had unlimited access to straw and branches. During nest building all the gilts used straw and a ll the experimental gilts also used branches. In the experimental group the interval from termination of nest building to birth of the first piglet (B FP) was significantly longer than in the control group (132 versus 58 min, P = 0.04). In the experimental group, nest-building behaviour was also perf ormed by fewer individuals during the interval from BFP until 2 h after tha n in the control group (38% Versus 71% of the gilts, P = 0.03). Gilts that performed nest building during this interval carried out more postural chan ges (P < 0.001) and spent less time in lateral recumbency (P = 0.001) than gilts which did not perform nest building. On average, gilts that performed nest building behaviour after BFP (n = 26) spent 54% of the first 2 h of p arturition in lateral recumbency and carried out 16 postural changes. Gilts that did not perform nest building behaviour during this interval (n = 16) spent 85% of the time in lateral recumbency and carried out five postural changes. In 10 gilts that were selected randomly from the experimental grou p nest building was studied in more detail. In these gilts nest building pe aked between 17 and 6 h prepartum. There was no difference in amount of beh aviour directed towards straw and amount of behaviour directed towards bran ches. The results indicate that the termination of nest building in sows is under environmental feedback control. When only straw was provided the nests did not have much of a lasting structure. However, when gilts had access to st raw and branches more structured and functional nests could be built. These nests may have been more effective in reducing the motivation for nest bui lding prior to the onset of parturition. (C) 2000 Elsevier Science B.V. All rights reserved.